Studies on cysteine conjugate β-lyase and thiol s-methyltransferase in insects

Cysteine conjugate β-lyase activity was demonstrated in the cuticle of M. sexta and H. virescens and was present in the cytosolic fraction from both of these species. Enzymatic activity was significantly decreased following each molt of the larvae and the increased until the start of the next instar. β-Lyase activity increased for 20 h after eclosure in the adult and the highest larval activity was measured in the late fifth instar. The insect enzyme appears to be less sensitive to (aminooxy)acetic acid, a cysteine conjugate β-lyase inhibitor, than was reported for the rat renal enzyme. Thiol S-methyltransferase activity was also localized in the cuticle of both insect species but was present in both the microsomal and cytosolic fractions.